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    <title>Document</title>
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  <script>
    /* 
        JS中，函数也是一个对象(一等函数)
            别的对象能做的事情，函数也可以
    */
    function fn(a) {
      console.log(a, "a");
    }
    let obj = { name: "孙悟空" };
    function fn2() {
      console.log("我是f2");
    }
    fn(fn2);
  </script>
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